C 程序帮助输入大写第一个字母

Question

我是一名初学者，正在编写一段代码

asks for the user's name

check if the length is >15, if it is, it will ask the user to input a shorter name when they restart the program

if the length is valid, upper case the first letter of the entered name

display something like "Hi name"

但是，无论我输入什么，程序都会一直退出。这是我所做的:

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <conio.h>

int main(void)
{
    char str_name[15];

    printf("Please enter your first name to begin: ");
    scanf_s("%14s", str_name, _countof(str_name));
    getchar();
    
    if (strlen(str_name) > 15)
    {
        printf("The entered name is too long, please restart the program and try again.");
        getchar();
        exit(0);
    }
    else
    {
        str_name[0] = toupper(str_name[0]);

        printf("Hi %s.\n", str_name);
        getchar();
    }
    
    return 0;
}

Answer 1

您可以简单地使用 fgets()读取输入缓冲区。

char *fgets(char *str, int n, FILE *stream) reads a line from the specified stream and stores it in a buffer pointed to by str. It stops when either n-1 characters are read, the newline character is read, or the EOF is reached.

关于fgets()的一些注意事项:

• 出错时返回 NULL。
• 在缓冲区末尾附加 \n 字符。可以用 \0 代替。
• 缓冲区必须是指向字符数组的指针。分配在堆栈或堆上。
• 从 stdin 或 FILE 对象中读取。

下面是一些示例代码，说明了这一点:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

#define NAMESTRLEN 16

int main(void) {
    char str_name[NAMESTRLEN] = {'\0'};
    size_t slen;

    printf("Please enter your first name to begin: ");
    if (fgets(str_name, NAMESTRLEN, stdin) == NULL) {
        fprintf( stderr, "Error from fgets()\n");
        return 1;
    }

    slen = strlen(str_name);
    if (slen > 0 && str_name[slen-1] == '\n') {
        str_name[slen-1] = '\0';
    } else {
        fprintf( stderr, "Too many characters\n");
        return 1;
    }

    if (str_name[0] == '\0') {
        fprintf( stderr, "No name entered\n");
        return 1;
    }

    str_name[0] = toupper((unsigned char)str_name[0]);

    printf("Hi %s.\n", str_name);

    return 0;
}